Effects of Physical Disturbances on BioSand Filters Used for Point-of-Use Water Treatment

Abstract

<p>Over 750 million people, 80% of whom live in rural communities, lack access to improved water sources. Even where an improved water source is easily accessible, recontamination and/or inadequate infrastructure may make it unsafe for human consumption. A lack of safe water leads to elevated rates of waterborne diseases and can exacerbate cycles of poverty by forcing individuals to miss school and work and to travel greater distances to secure better-quality water. Households in rural and remote communities may thus choose to use point-of-use treatment as a means of gaining greater control over their water quality and the health of their families. The BioSand Filter (BSF) is one such technology: it is an intermittently-operated household-scale slow sand filter currently used in over 70 nations around the world.</p> <p>This thesis situates point-of-use water treatment, and specifically the BSF, within the context of the relationship between water and health and the continuum of technologies used for water treatment. From this foundation, it presents the methodology and results of a study carried out to inform best-practices around BSF use by: (a) examining the effects on BSF media and filtration performance of physical disturbances that may commonly occur in the field; and (b) assessing whether the biological community within BSFs promotes nitrification that could produce elevated nitrate/nitrite levels.</p> <p>Results demonstrated that disturbing the filters through moving and side impacts caused marked sand compaction and decreased flow rates for plastic (Hydraid) BSFs. Although these decreased flow rates may contribute to user frustration and disuse, they were not associated with reduced filtration performance. Nitrate and nitrite concentrations were well below WHO guidelines for all samples, but changes in nitrogen speciation suggested that nitrification was mediated by the biological community within the filters. Recommendations for practitioners and for future research are discussed in light of these findings.</p>